1. Field of the Invention
The present invention relates generally to a durable, multiple-use needle-less (or needle-free) hypodermic jet injection device, and to methods of its making, operation, and use. More particularly, this present invention relates to such a device and to such methods which provide improved facility for use by user, especially for a user whose hands my be feeble or arthritic, and also for improved manufacturability, and further for improved effectiveness of use and operation in effecting a needle free hypodermic jet injection.
2. Related Technology
Needle-less or needle-free hypodermic jet injection devices have been in commercial use for over 40 years. A number of these devices have used pressurized gas to power a hypodermic jet injection. The related technology includes a number of teachings for gas-powered injection devices, including: U.S. Pat. No. 4,596,556, issued Jun. 24, 1986 to J. Thomas Morrow, et al.; U.S. Pat. No. 4,913,699; issued Apr. 3, 1990 to James S. Parsons; and U.S. Pat. No. 5,730,723, issued Mar. 24, 1998, to Thomas P. Castellano, et al. WIPO publication WO 97/37705 also discloses a gas powered disposable needle-less hypodermic jet injector.
The Morrow, et. al. ""556 patent is believed to teach a reusable hypodermic jet injection device in which a housing receives a shell or cartridge having a bore leading to a discharge aperture. Within the bore is received both a plunger sealingly engaging the bore, and a pressurized gas cylinder which rests against the plunger. The injection device includes a ram which has a penetrating tip confronting a penetrable wall section and seal of the gas cylinder, and a discharge mechanism for driving the ram through the penetrable wall section of the gas cylinder when a trigger device is released. Discharge of the pressurized gas from the cylinder drives the plunger to effect a jet injection, and also drives the seal of the gas cylinder to effect resetting of the discharge mechanism. The shell with its plunger, and spent gas cylinder, is discarded after an injection; and a new shell pre-filled with medication and with a new gas cylinder is used for each injection.
The Parsons ""699 patent is believed to teach a single-use jet injector which is totally discarded after one use. This injector is believed to have a body with a pair of gas chambers separated by a breakable valve. One of the gas chambers contains a pressurized gas, while the other chamber is sealingly bounded by a piston which drives a plunger. The plunger sealingly bounds a chamber into which a dose of medication is loaded by the user before the injection. This medication dose chamber leads to an injection orifice so that when the valve is broken, the piston and plunger are moved by pressurized gas communicated to the second chamber, and the plunger drives the medication forcefully out of the injection orifice to form an injection jet. After a single use, the device is discarded.
The Castellano ""723 patent, which was issued in 1998 and which does not cite the earlier Parsons ""699 patent, is believed to teach substantially the same subject matter as Parsons et al.
WIPO publication WO 97/37705 published pursuant to a Patent Cooperation Treaty (PCT) application for joint inventors Terence Weston and Pixey Thornlea, is believed to disclose a disposable hypodermic jet injector in which the device is powered by a gas pressure spring of the type common in the tool and die art as a substitute for the conventional metal spring-powered ejector pin. In the Weston device, the ram of the gas pressure spring is held in a contracted position by a trigger mechanism. When the trigger mechanism is released, the gas pressure spring is supposed to expand and drive a piston sealingly received in a bore and leading to a fine-dimension orifice in order to produce a jet hypodermic injection from liquid held in the bore ahead of the piston.
The Weston device is thought to have several deficiencies: such as difficult and costly manufacturing and sterilization processes, because pressurized gas and a drug dose need to be contained in the same package; and including a possible inability to endure long-term storage while still retaining the gas pressure in the gas spring to power an injection, and also maintaining the medication integrity. In other words, the gas pressure spring of the Weston device contains only a small quantity of gas, and depends upon the sealing relationship of the ram of this spring with a cylinder within which the ram is movably and sealingly received in order to retain this gas pressure. Even a small amount of gas leakage over time will be enough to render this injector inoperative.
In view of the above, it is desirable and is an object for this invention to provide a needle-less jet injection device which reduces the severity of or avoids one or more of the limitations of the conventional technology.
Thus, it is an object of this invention to provide a durable, needle-free gas-powered hypodermic jet injector providing for greater and improved ease in loading and operation for a user, particular for a user whose hands may be feeble or arthritic. In this respect, the present invention provides a more easily usable mechanism for drawing into and measuring a dose of medication within the injector device.
Further, this present invention provides an improved facility for a user to load and unload a pressurized gas capsule into and from the device.
Still further, a unique valving mechanism of the injector is especially configured for improved manufacturing, and for a concomitant improved reliability and durability in use of the device.
Further, the present invention improves the effectiveness of the formation of a high velocity hypodermic injection jet utilizing a source of pressurized gas that is controllably released from a pressurized gas capsule. That is, the present device avoids the shortcoming of allowing the pressurized gas to expand to a greater volume and lower pressure before significant energy from the gas is transferred to a dose of liquid medication in order to force the medication through a fine dimension orifice to form a hypodermic injection jet. Because the pressurized gas is utilized at the smallest practicable volume and highest practicable pressure level, the essential energy transfer from the pressurized gas to the liquid medication is effected most expediently and most effectively to provide the greatest possible velocity and energy level in the hypodermic injection jet.
Accordingly, an embodiment of the present invention provides a jet injection device comprising: a device body having a forward end; an injection cylinder at the forward end of the device body, and the injection cylinder having a cylinder bore in which an injection piston is sealingly movable to cooperatively define a variable-volume chamber for holding a dose of liquid medication; the injection cylinder defining a fine-dimension injection orifice in liquid flow communication with the variable-volume chamber to receive and discharge liquid medication as a forceful high velocity jet upon forceful movement of the injection piston in the cylinder; a power source in the device body for forcefully moving the injection piston in the cylinder in response to communication of gas pressure to a gas pressure piston; the power source including a source of pressurized gas for selective communication with the gas pressure piston; a trigger assembly for selectively effecting communication of pressurized gas from the source to the gas pressure piston; and a lost motion preventing mechanism selectively drivingly connecting the gas pressure piston to the injection piston.
According to a further aspect this invention provides: a method of providing a gas powered hypodermic jet injection device, the method comprising steps of: providing a device body having a forward end; providing an injection cylinder at the forward end of the device body, disposing sealingly in the injection cylinder an injection piston to cooperatively define a variable-volume chamber for holding a dose of liquid medication; providing the injection cylinder with a fine-dimension injection orifice in liquid flow communication with the variable-volume chamber, and utilizing the injection orifice to receive and discharge liquid medication as a forceful high velocity jet upon forceful movement of the injection piston in the injection cylinder; providing a power source in the device body for forcefully moving the injection piston in the cylinder in response to communication of gas pressure to a gas pressure piston; providing for the power source to include a source of pressurized gas for selective communication with the gas pressure piston; providing a trigger assembly for selectively effecting communication of pressurized gas from the source to the gas pressure piston; and configuring the device body to define an axially elongate recess opening along a side thereof, providing a door member in a first position closing the recess and the door member opening to a second position to reveal the recess and a penetrator member disposed within the recess; providing for the recess to be sized and configured to accept a pressurized gas capsule including a penetrable diaphragm portion and an end surface opposite to the penetrable diaphragm portion; including on the door member a camming surface engaging the end surface, and in response to closing of the door member from the second position to the first position utilizing the camming surface to move the pressurized gas capsule fully into the recess and to be impaled at the penetrable diaphragm portion upon the penetrator member.
Additional objects and advantages of this invention will appear from a reading of the following detailed description of two exemplary preferred embodiments of the invention, taken in conjunction with the appended drawing Figures, in which the same reference numeral is used throughout the several views to indicate the same feature, or features which are analogous in structure or function.